Hydrothermal deposition of titanate on biomass carbonaceous aerogel to prepare novel biomass adsorbents for Rb+ and Cs+

Cellulose nanofibril/titanate nanofiber modified with CdS quantum dots hydrogel with 3D porous structure: A stable photocatalytic adsorbent for Cr(VI) removal

A novel cellulose nanofibril/titanate nanofiber modified with CdS quantum dots hydrogel (CTH) was synthesized as an effective, stable, and recyclable photocatalytic adsorbent using cellulose nanofibril (CN), titanate nanofiber (TN), and CdS quantum dots. Within the CTH structure, CN formed an essential framework, creating a three-dimensional (3D) porous structure that enhanced the specific surface area and provided abundant adsorption sites for Cr(VI). Simultaneously, TN modified with CdS quantum dots (TN-CdS) served as a nanoscale Z-type photocatalyst, facilitating the efficient separation of photoinduced electrons and holes, further increasing the photocatalytic efficiency. The morphological, chemical, and optical properties of CTH were thoroughly characterized. The CTH demonstrated the maximum theoretical adsorption capacity of 373.3 ± 14.2 mg/g, which was 3.4 times higher than that of CN hydrogel. Furthermore, the photocatalytic reduction rate constant of the CTH was 0.0586 ± 0.0038 min-1, which was 6.4 times higher than that of TN-CdS. Notably, CTH displayed outstanding stability, maintaining 84.9 % of its initial removal efficiency even after undergoing five consecutive adsorption-desorption cycles. The remarkable performance of CTH in Cr(VI) removal was attributed to its 3D porous structure, comprising CN and TN-CdS. These findings provide novel insights into developing a stable photocatalytic adsorbent for Cr(VI) removal.

Computer chip-inspired design of nanocellulose/carbon dots hydrogel as superior intensifier of nano-sized photocatalyst for effective Cr(VI) removal

Hydrogel, a common carrier of photocatalyst that suffers from compromised catalytic efficiency, is still far from practical application. Herein, based on "computer chip-inspired design", a novel nanocellulose/carbon dots hydrogel (NCH) was fabricated as superior intensifier instead of common carrier of sodium titanate nanofibre (STN), where carbon dots (CDs) enhanced amino group-induced adsorption for Cr(VI), promoted photocatalytic properties of STN via transferring the photogenerated electron-hole pairs and improved amino group-induced desorption for reduced product (Cr(III)) via electrostatic repulsion, showing an efficiency of 1 + 1 > 2. Adsorption and photocatalysis experiments demonstrated superior removal performance of the NCH incorporating STN, as shown by theoretical maximum adsorption capacity of 425.74 mg/g and kinetic constant of 0.0374 min^-1 in the photocatalytic process, which was nearly 6.6 and 7.3 times of STN. A series of experiments was conducted to confirm the novel mechanism of CDs-enhanced adsorption-photocatalysis-desorption synergy. This work not only provides new insights into the fabrication of a superior intensifier for nanosized photocatalyst, but also proposes one new mechanism of CDs-enhanced adsorption-photocatalysis-desorption synergy, which is helpful for designing and optimizing nanosized photocatalyst.

Selective Removal of Boron from Aqueous Solutions Using ECH@NGM Aerogels with Excellent Hydrophilic and Mechanical Properties: Performance and Response Surface Methodology Analysis

The remediation of environmental boron contamination has received extensive research attention. The adsorbent ECH@NGM aerogel with high hydrophilic and mechanical properties was synthesized to remove boron. The ECH@NGM aerogel had a high adsorption capacity of 81.11 mg/g, which was 14.50% higher than that of commercial boron-selective resin Amberlite IRA743. The Freundlich model and pseudo-second-order model described the adsorption behavior well. In addition, the response surface methodology (RSM) could predict the experimental outcomes and optimize the reaction conditions, and X-ray photoelectron spectroscopy (XPS) and control tests were utilized to investigate probable adsorption mechanisms. These data showed that the B ← N coordination bond was the primary adsorption force. The adsorbent had good resistance to interference from coexisting salts, high reusability, good adsorption performance even after five reuse cycles, and a high desorption rate in a relatively short time. The adsorption performance in real brines could be maintained at 80%. Therefore, this work not only provided ECH@NGM aerogels for the removal of boron from brine but also elucidated the main adsorption processes between N-containing adsorbents and boron, facilitating the design of future adsorbents for boron removal.

Remediation of heavy metal polluted waters using activated carbon from lignocellulosic biomass: An update of recent trends

The use of a cheap and effective adsorption approach based on biomass-activated carbon (AC) to remediate heavy metal contamination is clearly desirable for developing countries that are economically disadvantaged yet have abundant biomass. Therefore, this review provides an update of recent works utilizing biomass waste-AC to adsorb commonly-encountered adsorbates like Cr, Pb, Cu, Cd, Hg, and As. Various biomass wastes were employed in synthesizing AC via two-steps processing; oxygen-free carbonization followed by activation. In recent works related to the activation step, the microwave technique is growing in popularity compared to the more conventional physical/chemical activation method because the microwave technique can ensure a more uniform energy distribution in the solid adsorbent, resulting in enhanced surface area. Nonetheless, chemical activation is still generally preferred for its ease of operation, lower cost, and shorter preparation time. Several mechanisms related to heavy metal adsorption on biomass wastes-AC were also discussed in detail, such as (i) - physical adsorption/deposition of metals, (ii) - ion-exchange between protonated oxygen-containing functional groups (-OH, -COOH) and divalent metal cations (M²⁺), (iii) - electrostatic interaction between oppositely-charged ions, (iv) - surface complexation between functional groups (-OH, O^2-, -CO-NH-, and -COOH) and heavy metal ions/complexes, and (v) - precipitation/co-precipitation technique. Additionally, key parameters affecting the adsorption performance were scrutinized. In general, this review offers a comprehensive insight into the production of AC from lignocellulosic biomass and its application in treating heavy metals-polluted water, showing that biomass-originated AC could bring great benefits to the environment, economy, and sustainability.

TriMOF synergized on the surface of activated carbon produced from pineapple leaves for the environmental pollutant reduction and oxygen evolution process

Facile and modest synthesis of significantly effective and less-cost catalysts for environmental pollutant degradation and oxygen evolution holds substantial potential in environmental and energy fields. Hereby, Trimetallic organic frameworks (TriMOF) consisting of Fe, Co, and Zn synergized on the surface of activated carbon (AC) from pineapple leaves tend to show exponential catalytic activity due to the more excellent ionic conductivity, catalytic stability and multiple active sites provided by different metal precursors. Furthermore, the developed nanocomposite was coated on the stainless-steel electrode substrate at room temperature, delivering greater electrocatalytic surface area and numerous active sites. The oxidation reaction kinetics drives the catalytic reduction of 4-nitrophenol to 4-aminophenol with a minimal time of 12 min @ >97 % efficiency. Furthermore, on electrocatalytic oxidation of water splitting process due to the presence of multiple metallic, active sites, the overpotential is at 370 mV having Tafel slope of 40 mV/dec and electrochemically active surface area of is 9.9 mF/cm². This superior catalytic reduction of 4-nitrophenol and electrocatalytic water oxidation process is attributed to the developed composite's active centre and conductivity.